X-ray inspection of bodies



March 5, 1946. v M, ZAPP -2,396,069

\ X-RAY INSPECTION OF BODIES Filed Oct. 2,. 1943 I N V EN TOR. Ifiarfi/a/r M ZAP/ Patented. Mar. 5, 1946 UNITED STATES PATENT OFFICEFrederick M. Zapp, Brooklyn, N .1, assignor to Fairchild Engine andAirplane Corporation, Farmingdale. N. Y., a corporation of MarylandApplication October 2, 1943; Serial No. 504,662 10 Claims. (-Cl.-250 3)This invention relates to methods and means for the examination ofbodies to determine the presence and location offlawstherein, andrelates particularly to the X-ray examination of bodies formed ofdissimilar materials.

It is frequently of great importance in the manufacture of engines,bearings, and other machine parts or manufactured products wherein thereis a bond between dissimilar materials, to inspect the bond to determinewhether it is complete and sound or is standing up under the conditionsof use. Thus, for example, when manufacturing aeroplane motors having asteel sleeve or cylinder barrel on which an aluminum muff has been castforthe machining of cooling fins of,

the engine; it is important to insure the formation and preservation ofa complete'and adequate bond between the different metals.

Flaws or cracks in the bond between the aluminum muii and steel sleevenot only weaken the structure but greatly decrease the heat transferfrom the cylinder to the coolingfins. Moreover, if such flaws exist, theeffect thereof is increased on heating and expansion of the metalsysincethe aluminum has a greater coefficient of expansion than the steel andtends to enlarge any cracks or non-conducting areas.

No satisfactory method or means has existed heretofore for theinspection of bonds or areas of this character.

In accordance with the present invention, the desired inspection iseffected by means of -X-rays and the operation is carried out by methodsand means which not only indicate the presence of an imperfect bondbetween the materials, butalso indicate the location and extent of theimperfection. Furthermore, the present invention renders it possible tolocate flaws and cracks or imperfections which aresominuteor latent asto be incapable of detection by prior means of inspection as well'as anyspong'iness in the aluminum muff or other imperfections in the metalsu'nder object under inspection so as to definitely locate the positionand extent of any imperfection in the product.

One of the objects of the invention is to provide novel methods andmeans for the X-ray examination of bodies. Another object of theinvention is to provide methods and means for examination of bondsbetween materials having difierent'coefilcients of expansion. I

a A further object of the invention isto provide improved methods andmeans for the examination of areas of a body which are concentric withan axis of the body.

A specific object of the invention is to simplify the examination'ofconcentric cylinders of different metals to determine the character andaction of the bond therebetween.

'These and other objects and features of the invention will appear fromthe following description thereof in which reference'is made to thefigures of the accompanying drawing.

" In the'drawing:

Fig. 1 is a diagrammatic plan view of one form of mechanism embodyingthe'present invention;

Fig. 2 illustrates a typical exposed film produced withthe mechanism ofFig. l; and

Fig. 3 is a diagrammatic illustration of an alternative embodiment ofthe present invention.

In that form of the invention illustrated in Fig. l, the article to beexamined is shown as an engine cylinderhaving'a steel sleeve 2' with analuminum muff 4'bonded to the sleeve. The bond between the steel andaluminum is shown at 6 and represents the area to be examined. Asuitable source of' X-rays is indicated at 8 and a thata beam of X-raysM will pass through the slot 12 and through the engine cylindertangensensitive film or screen and if de'sired, the body and screen maybe moved in a coordinated mannor toassociate the exposure of differentportions of the screen with particular portions of the tial to the bond6 between the sleeve 2 and'the aluminum muff 4.

An X-ray senstiive film or screen I6. is located in position to receiveX-rays after they have passed the bond 6 so a to record the conditionnum or other flaws in either metal they will be shown up by the X-rays.

Since any cracks in the bond may be very small and therefore dificult toidentify or observe, the whole body may be heated or heat may be appliedonly to the aluminum muff on the exterior of the sleeve so as to causethe aluminum to expand to a greater extent than the steel sleeve. Thecrack will then be opened up appreciably or cracks may be produced inweakened areas which would not withstand the conditions under which theengine will be used. The enlarged cracks pass a greater portion of theX-rays than smaller, hair-line cracks, or a weakened bond, and thusinsure suilicient exposure of the screen or film to render small orlatent imperfections more easily observable.

The whole body may be heated by any suitable means, such as the heatingelement I 9, or, if desired, a difference in expansion of the metals ormaterials may be established by heating or cooling one metal to agreater extent than the other. The metals may be readily cooled by meansof a cooling medium such as Dry Ice, or the like; When examining abearing or other object in which the metal having the greatercoefficient of expansion is located on the interior of a metal of lowerexpansion Dry Ice or a cooling medium may be located in the center ofthe body. The manner in which the object is heatedv or cooled should inany case be such as to cause the bond or joint between the materials toopen up and thus ofier less resistance to the passage of X-raystherethrough.

In order to examine a complete cylinder or other object having a bondconcentric with an axis of the body, it is necessary to rotate orotherwise move the body and screen so that the full extent of the bondmay be inspected. This may be accomplished by mounting the cylinder on asuitable support and rotating it about its axis 22 while keeping thearea to be examined in the beam of X-rays and between the source ofX-rays and the screen. The location and extent of the crack orimperfection in the bond or other flaws in the product can be determinedby moving the film or screen relative to thecylinder so 1 as to obtain acontinuous or intermittent series of exposures which serve to record thecondition of each or a plurality of sections of the bond underinspection.

By moving the cylinder and film IS in a coordinated manner with respectto the beam of X-rays i4 successive and predetermined portions of thefilm may be exposed to show the condition of successive andpredetermined areas of the bond. A typical exposed film produced in thismanner is illustrated in Fig. 2 wherein the area 18 corresponds to aperfect section of the bond and the areas 20 indicate over-exposurescorresponding to cracks in the bond.

As shown in Fig. l, the film I6 is mounted on a cylindrical support 24rotatable about an axis 26 parallel to the axis 22 about which thearticle to be examined is rotated. The film is shielded by a stationarylead sheath 28 having a sight opening 30 through which it is exposed tothe beam of X-rays. The support 24 may itself be formed of lead orshielded to prevent the X-rays passing through the sight opening 39 fromexposing the film a second time as it passes the side of the cylinderoppositethe sight opening.

The movement of the object to be examined and the film I6 are preferablycoordinated by suitable means such as the shaft 32 and worms 34 and 36,so that the speed of movement of the bond 6 and that of the film areequal or related. The location of any dark or over-exposed areas on thefilm will then correspond to the location of any cracks between thesleeve and muff or other imperfections in the piece being examined.

Instead of rotating the film it may be supported in a cassette 38 asshown in Fig. 3 and moved in a vertical plane past the sight opening 40in the lead shielding tracks 42. A further lead shield :4 also may beprovided to aid in limiting the X-ray radiation passing toward the filmand thereby reduce fogging of the film by stray X- rays. Movement of thefilm and cassette may be coordinated so as to advance the film only onehalf as rapidly as the bond rotates so that the area of any flaws in thebond will be concentrated and brought out more distinctly on the film.

In either form of the invention the exposure of the film and themovement of the cylinder may be continuous or in successive steps.Continuousmovement of the cylinder and film speeds up the inspectionoperation whereas step by step inspection can be carried out withsimpler equipment.

The constructions described not only indicate the location and characterof flaws in the bond but they also indicate the presence and location ofimperfections such as spongy areas in the aluminum mufi. The latter willpass X-rays more readily than sound metal and'the record on the filmwill show two areas corresponding to the increase in radiation permittedwhen the spongy area intercepts the beam of X-rays at the front andagain at the rear of the are through which it travels past the X-raybeam.

It is usually preferable also to use X-ray sensitive film instead of afluorescent screen or other means giving a transient record of the piecesince the record can then be attached to the piece as it passes throughthe plant or is returned for repair or further inspection. Moreover, thecontrast in areas of the film can be made more pronounced by prolongedexposure so as to increase the density of the areas of the film showingthe location of imperfection.

While the forms of the invention shown in the drawing include acylindrical support and a cassette for the film, any other form ofsupport may be used and the elements employed for moving the object andfilm or for coordinating their movement may be varied as desired withoutdeparting from the spirit and scope of the invention.

I claim:

1. A method for theexamination of curved bonds between materials havingdifferent coefficients of expansion which comprises the steps ofsubjecting the materials to temperature conditions which tend toseparate the materials at the bond, passing X-rays through the bondtangential thereto, and registering the condition of the joint on anX-ray reactive screen.

2. A method for the examination of curved bonds between materials havingdifferent coefficients of expansion which comprises the steps of heatingthe materials until they tend to separate at the bond, passing X-raysthrough the bond tangential thereto, and registering the condition ofthe bond on an X-ray reactive screen.

3. A method for the examination of curved bonds between materials havingdifierent coefficients of expansion which comprises the steps of heatingthe material having a higher coeficie'nt of expansion until it tends toseparate from the other material a at the bond, passing X-rays throughthe bond tangential thereto, and registering the condition of the bondon an X-ray reactive screen.

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4. A method for the detection of flaws in a which comprises the steps ofrotating said body 1 about said axis, subjecting said materials totemperature conditions which tend to separate said materials, andpassing X-rays through said body tangential to the path of movement 01the bond and onto an X-ray sensitive surface.

6. A method for the examination oi. a body having a bond betweendissimilar materials located concentric with an axis of the body which 7comprises the steps of heating said body until said materials tend toseparate at said bond, rotating said body about said axis, passing abeam of X-rays tangentially through said bond, moving an X-ray sensitivescreen with respect to said beam at a speed corresponding to the speedof movement of said bond, and shielding said screen from X-rays exceptat a narrow zone in alignment with said bond, whereby the position ofdifierently exposed portions ofthe screen will bear a predeterminedrelation to the position of definite portions of said bond.

7. Apparatus for the inspection of bonds between dissimilar portions ofa body having the form of a surface of revolution, comprising means forrotating said body about its axis, means for generating X-rays, meansfor moving an X-ray sensitive means in a manner coordinated with themovement of the body, and shielding means interposed between saidrotating means and said X-ray sensitive means, having a narrow X-raypervious portion permitting substantially only those X-rays passingthrough said bond to im pinge upon said X-ray sensitive means.

8. Apparatus for the inspection of bondsbetween dissimilar portions of abody having the form of a surface of revolution, comprising means forrotating said body about its axis, means for generating X-rays, a filmholder rotatable about an axis parallel to the axis of said body, meansfor coordinating the speed of rotation of said body and holder, andshielding means interposed between said holder and said rotating meanshaving a narrow X-ray pervious portion in alignment with said X-raygenerating means and said bond.

9. Apparatus for the examination of a bond between metals havingdifferent coeiiicients of expansion and located in an area concentricwith an axis of a body comprising means for subjecting said body totemperatures which tend to separate said metals at the bond, means forrotating said body about its axis, means for passing X- rays throughsaid body tangential to said bond, movable X-ray sensitive meanspositioned to receive X-rays after they have passed through said bond,means for coordinating the movement of said X-ray sensitive, means andsaid body rotating means, and shielding means interposed between saidX-ray sensitive means and said body rotating means, said shielding meanshaving a narrow X-ray pervious portion in alignment with said bond.

10. Apparatus for the examination of a bond between metals havingdifferent coefiicients of expansion and located in an area concentricwith an axis of a body comprising means for subjecting said body totemperature which tend to separate said metals at the bond, means forrotating said body about its axis, means for passing X-rays through saidbody tangential to said bond, X-ray sensitive means positioned toreceive X-rays after they have passed through said bond, means formoving said X-ray sensitive means in a manner coordinate with themovement of said body, and shielding means interposed between said X-raysensitive means and said body rotating means having a narrow X-raypervious portion substantially in alignment with said bond and thesource of X-rays.

FREDERICK M. ZAPP.

